A 58-year-old male patient, previously healthy, with no history of drug use, presented with a 2-month history of weight loss, headache and asthenia.
The blood count showed hemoglobin of 13.9 g/L, platelets of 183 x 109/L and leukocytosis of 16.1 x 109/L with 65% of eosinophils (absolute eosinophil count (AER): 10.465 x 109/L.
She reported no history of allergies, atopy, or asthma.
The stool test was negative.
The markers of myocardial damage (troponins) were normal.
Bone marrow biopsy and myelogram showed bone marrow infiltration by mature eosinophils, with no cells outside the bone marrow.
Treatment was initiated with hydroxyurea up to 1.5 g a day without a satisfactory decrease in the eosinophil count, so it was decided to add prednisone 40 mg/day, without improvement of the response.
The presence of transcripts of the FIP1L1/PDGFRA fusion product in peripheral blood was studied by qualitative polymerase chain reaction (PCR), which was positive.
Imatinib 100 mg/day was started with rapid and progressive reduction of AER until normalization after the second week of treatment.
Anemia (Grade 2) was detected at the beginning as an adverse reaction, which resolved when the dose was reduced to 400 mg/week, without loss of clinical response or cure.
After one year of follow-up, the patient remains asymptomatic, with no evidence of target organ damage, with normal haemoperipheral figures and AER (always < 0.5 x 109/L) and no imatinib dose adjustments.
